Pneumatic inner tube and method of making it



which the tubes are cured. Heated gas, such as nitrogen or carbon dioxide, produces most satisfactory results for this purpose.

The coating lms, when thus applied to the inner tubes, adheres so firmly to the surface of the tubes that they appear to be blended with the rubber constituting the main body of the tube and for that reason, the tubes may be stretched and flexed without any tendency to cause separation between the lm and the rubber upon which the latterfisf Also,v inv spite" of repeated.;'stretchingA andi` flexing, the continuity of the iilm is not broken. Therefore, the imperair or other gases, is unirnpa i r ed v and a bead diameter of 19 inches was determined by inilating the tube when `enclosed... \t i t l 1in ,a

' ftliereof, said' coating being substantially coexten- 'sive' with said surface and comprising a composistandard tire casing to a pressure' of A35l per square inch. The tube was left stan a period 24 days, after which the press lfor - period@ Eveny this-.slight losswas probablyaccounted for by reason of the escapeof. air zthrough. the valve of .the tube when the gauge was-applied for purposes iofiideterminmg the pressuregii'f 7;; In a similar tirecontaining 4an inner tube iden'- tical in construction exceptfor Ithe'omission cf the coating films, the `pressure drop, at the end of ayffperi'Qd4 amounted -to 14' pounds per tliejersidl of thatestuponi the S11-liefs" inch.'

l .dY- been, indicated; .the gelatin appears Sto he' prinfci'rial4 cas-Stopping? agent. hellatxmay be' .eii'rlr'ds pens'ed withior it'fl'ria'y' be 'replaced by artificial suspension of; bber;` such as 'the ordinary ce'- I'I'ientfriffjrubbl H'gasjolineon'rubber and `benvcene. `H ever, 'jfis 'alwaysdesirable toiretain a" suta plastic1Zing`-., agent; j sucli' as Ipolyglyc- 'eroLJfIurkey red' "`oil; orL sjii'nilar'frnaterial the geiatinjnii. while the previously described lnjis, gelatin 'constituted the*l principal agent, it isf understood" that'jmaterialsjhaving similar properties `may'g'fI in some cases,` bel substituted therefor] with fairly Satisfactory results." For eamrillele; aseinhswglbih rfother, itl.- fqining hyur'ophyuie 'centres or Sinclar character may, if 'properly plasticizedvbyjpolyglycer- 011.011. similetfasena he @plagada Where-these Sibstae are; employed; es @aime media ,ii hiehirdsireblef that-fthe Pressure 11.11141 .conte-9i: iglwitb thecoatedlsurface dur-ins @reubsequentiusesof. the.articles,belsubstantially free fromvwater andlwater .vapor in: Qrder to vprevent Ther newC-'coatingl medium' is l inexpensive to prepare and may be applied to the surfaces of the inner tubes with great ease. In view of the high efficiency thereof as means for preventing the escape of inflating gas, its use is highly desirable from a commercial viewpoint.

Although I have disclosed only the preferred forms of the invention and have described those forms in detail, it will be apparent to those skilled in the art that the invention is not so limited but that various modifications may be made therein without departing from the spirit of the invention or fromthe scope of the appended claims.

meability of the lm to inflating media, suche rfalli/'hat I claim is:

.1. A pneumatic rubber inner tube for vehicle tires having a coating upon at least one surface thereof, said coating being substantially ccextensive with said surface and comprising a composiztion containing gelatin and a polyglycerol.

2. Atzpneumatic rubber inner tube for vehicle tireshavinga coating upon at least one surface tionfcontaining latex, gelatin and a plasticizing agemi- 333A pneumatic-'rubber inner tube for vehicle tires havng'a coating upon at least one surface thereof,'-s'aid coatingl being substantially ccextenrsive with, said surface and comprising a compositioncontaining latex, gelatin and a plasticizing agentsaid `coating further'comprising a plurality of i'llms,` the proportion of latex being gradually decreased and the proportion of gelatin gradually increased in each film from the inner to the outer nlm.

ffl-4. A pneumatic 'rubber inner tube for vehicle tires thatis to be substantially stretched during use said tube being coatedwith an extensible gas impervious lm capable of adhering closely and stretching with the tube without rupturing or separating from the tube.

5;; A pneumatic rubber inner tube for vehicle tires. that is'to be substantially stretched during use said tube being coated with an extensible gas impervious film capable of adhering closely and stretching with the tube without rupturing or separating from the tube, said coating containing a giel-forming hydrophyllic colloid and a plasticizer.,

' 6. A pneumaticrubber `inner tube for vehicle tires that is to besubstantially stretched during use said tube being coated with an extensible gas impervious' filmjcapable of adhering closely and stretching with the tube without rupturing or separating from the tube, said coating containing a jel-forming hydrophyllic colloid, rubber and a polyelyceroli j 7.'.A'pneumatic rubber inner tube for' vehicle tires capable of withstanding repeated stretching andv flexingzand coatedon at least one surface with ja. dried gas impervious film which will stretch andfflexjwithlthe tube without rupturing or separatingitherefrom, said coating containingLa jelforming colloid and polyglycerol. 8. -'A-`pneumatic rubber inner tube for vehicle tires' that is to be repeatedly stretched and ilexed in'use, which'includes an extensible gas imperviouslm adhered to at least one surface theref. said lm having been applied prior to the vulcaniz'atio'n of the rubberand being capable of retaining its adhesion to the tube throughout repeated stretching and flexing.

'VQ'.C'The'method of making a pneumatic rubber i'nnerftubelfor vehicle tires which comprises disposing the tube containing the usual compounding ingredients in an uncured state upon a mandrel, applying to the exposed surface of the tube `a gelatin-containing lm in a Vehicle, then after substantially complete evaporation of the vehicle stripping the coated tube from the mandrel, turning it inside out, joining the ends and then subjecting the Whole to vulcanization.

10. The method of making a pneumatic rubber inner tube for vehicle tires which comprises disposing the tube containing the usual compounding ingredients in an uncured state upon a mandrel, applying to the exposed surface of the tube a gelatin-and-polyglycerol-containing lm in a Vehicle, then after substantially complete evaporation of the vehicle stripping the coated tube from the mandrel, turning it inside out, joining the ends and then subjecting the Whole to vulcanization.

11. The method of making a pneumatic rubherinner tube for Vehicle tires which comprises disposing the tube containing the usual compounding ingredients in an uncured state upon a. mandrel, applying to the exposed surface of the tube a jel-forming hydrophyllic colloid and a plasticizer, stripping the coated tube from the mandrel, turning it inside out, joining the ends and then subjecting the whole to vulcanization.

12. The method of making a pneumatic rubber inner tube for vehicle tires which comprises disposing the tube containing the usual compounding ingredients in an uncured state upon a mandrel, applying to the exposed surface of the tube a gelatin-latex-polyglycerol-containing film in a vehicle, then after substantially complete evaporation of the vehicle stripping the coated tube from the mandrel, turning it inside out, joining the ends and then subjecting the whole to vulcanization.

PAUL W. LITCHFIELD. 20 

